Download 1 Impact of road runoff in soil and groundwater. Synthesis of

Impact of road runoff in soil and groundwater.
Synthesis of Portuguese and other European case-studies
TERESA E. LEITÃO
PhD in Hydrogeology, Senior Research Officer at National Laboratory for Civil Engineering [email protected]
Groundwater Division of DHA/LNEC
Av. do Brasil, 101, P-1700-066 Lisboa, Tel. (+351) 21 844 3802
http://www.dha.lnec.pt/nas
Abstract Road circulation is capable of producing compounds that can pollute the
environment. The level and type of emissions depend on several technical aspects that can be
related with the road design and the vehicle engineer (size, type of fuel used), as well as with
operational factors that are related with the way that the vehicle is used.
The compounds emitted come from the fuel combustion, vehicle compounds use, road
accessories (like lateral crash barriers) degradation, road degradation, maintenance procedures
(application of chemicals), leakage, and accidents.
In this paper a synthesis of soil and groundwater pollution by heavy metals in the vicinity of
roads is presented. The results are based on data collected by LNEC as well as other data
gathered in published papers, summing more than three dozens of case-studies in 10 different
European countries.
The objective of this analysis was to compile as much information as possible about road
pollution by heavy metals in soil and groundwater, in order to be able to have a general
overview for Europe of the effective degree and extension of road pollution, independently of
the different conditions specific of each study area.
Key Words: road pollution; soil; groundwater; European case-studies.
INTRODUCTION
Traffic is a source of diffuse pollution with impacts in the environment that need to be
prevented or minimised. Cars, lorries, motorcycles, among other vehicles, are emitting heavy
metals (Pb, Zn, Fe, Cu, Ni, Cd, Hg, Cr), hydrocarbons (PAH, oil, fuels), nutrients (N, P),
particulates (clay and soil particles) and other organic matter (dust, dirt, humus) into the
environment (Table 1).
1
Table 1 Overview of pollutants originating from roads and traffic and their main sources (adapted from Gupta
et al., 1981a; Luker and Montague, 1994, and Leitão et al., 2000)
Type of pollutant
Heavy metals
Cadmium
Chromium
Copper
Lead
Zinc
Hydrocarbons
PAHs
Nutrients
Organic matter
Salts
Microbe
Particulates
Source of pollution
Tyres and brake pads, fuel, motor oil additives, rust, crash
barriers
Tyres, brake pads
Bearing, tyres, brake pads
Tyres, brake pads, radiators
Fuel, tyres, brake pads
Lubricating oils, tyres, brake pads, crash barriers
Oils, fuels, exhaust emission
Fuel, plastics, pavement
Fertilizers, motor fuel & oils, exhaust emission
Vegetation, litter, animal droppings
De-icing and fertilizers
Soil, litter, excreta, livestock movements
Tyre, brake & pavement wear, mud & dirt accumulated on
vehicles
The quantification and control of diffuse pollution sources is a requirement of the Water
Framework Directive, which states that member-states should address the water policy issues
in a coherent, holistic and sustainable approach. The mechanisms and pathways through
which diffuse pollutants from roads move through the environment are important
considerations in planning and targeting prevention and control measures.
The results presented hereinafter are a part of the information collected in case studies
analysed in LNEC since 1997, in the framework of EU studies, together with other
information collected in published papers. They refer to the knowledge gathered for the case
of heavy metals pollution dispersion in soils and water, in more than 3 dozen of case-studies,
in 10 different European countries.
IMPACTS OF HEAVY METAL ROAD POLLUTION IN THE SOIL AND WATER
The majority of studies on heavy metals in road runoff have concentrated on lead, cadmium,
copper, zinc and iron. Some studies have also included nickel, chromium and manganese. The
more unusual metals, such as titanium, vanadium, cobalt, arsenic, molybdenum, tin, tungsten
2
and antimony, are occasionally mentioned as trace constituents (James, 1999).
Metals in runoff can be attached to inert sediments, or be contained in immiscible fluids, or
occur as particles, soluble salts or insoluble compounds. Chemically they can be organic or
inorganic, compounds or complexes, and can usually exist amongst a variety of ionic species
depending primarily on the prevailing redox and pH conditions.
Soil is the media where the road pollution history is kept. Groundwater is a more
hydrodynamic media, subject to higher quality fluctuations over time, depending on
permeability properties of the media as well as chemical properties such as pH and CEC.
Heavy metals can be harmless in minute quantities. However, at high concentrations
biological life can be threatened. The following text presents some of the results gathered for
the studied heavy metals.
Cd is a very mobile element and the metal that more easily desorbs by ionic exchange
processes (Harrison et al., 1981; DWW, 1995; Reinirkens, 1996; Leitão et al., 2000, Pagotto
et al., 2001 & Diamantino, 2002).
The presence of Cd in soil and groundwater close to the roads is usually low, in
concentrations lower than the intervention1 and VMA2 defined, respectively. Nevertheless, its
presence due to road effects is clear (Fig. 1). In most case-studies the Cd concentration
decreases with distance to the road, and in several cases also with depth
1
For soil, the quality values used are defined in Dutch legislation (MHSPE, 1994) as target and intervention
For groundwater, the quality values used are defined in Portuguese legislation (DL 236/98, 1998) as
recommended (VMR) and admissible (VMA)
2
3
Cd (mg/kg) variation in soils close to the road, at 3 distances and 3 depths
Variação de Cd (mg/kg) em solos adjacentes a estradas, a 3 distâncias e 3 profundidades
Intervention value
Valor de Intervenção
(12 mg/kg)
(12 mg/kg) 12
- 37
countries
(P,SP,F,I,D,SW,NL,DK,UK,FIN)
- 37study
casoscases;10
de estudo;
10 países
(P, SP, F, I, D, SW, NL, DK, UK, FIN) --
max.
máx
upper quartile
quartil sup.
8
median
mediana
lower
quartil
inf.quartile
mín.
min.
4
Target value
Valor guia
(0.8 mg/kg)
(0,8 mg/kg)
0 -1 m
1-5m
2-10 cm prof.
depth
0-2 cm depth
prof.
10-30 cm depth
prof.
2-10 cm prof.
depth
0-2 cm depth
prof.
10-30 cm depth
prof.
depth
2-10 cm prof.
0-2 cm depth
prof.
0
20 - 30 m
Fig. 1 Cd variation in soils close to the road, at 3 distances and 3 depths
Cd presence can also be observed in the groundwater and interstitial water in the vicinity
of roads. It is possible to observe clear variations along the time and with distance to the road,
due to its high mobility, with some few samples exceeding the target value (Fig. 2). It is
possible to notice an increase of concentration after rain events.
Cd concentration in the road vicinity is not high once its initial amount in road dust is low.
Therefore, even if there are changes in the soil conditions (e.g. pH decrease) that promote Cd
mobility, it is not likely to find high Cd concentrations. Nevertheless, it is important to be
acquainted about Cd toxicity at very low levels and about its cumulative characteristics.
4
5
Cd (µ
µg/l)
4.5
July - Sept. 98
Oct. - Dec. 98
Jan. - Mar-99
April - Jun-99
4
3.5
3
VMA = 5 µg/l (6 µg/l)
VMR = 1 µg/l (0,4 µg/l)
2.5
2
(Dutch legislation
1.5
MHSPE, 1994)
1
0.5
P, Vila Real, IP4
P, Recta do Cabo, EN10
F, Erdre, A11
F, Houdan, RN12
D, Rud, M70
Fin, Utti, VT6
D, Vejenbrod, M14
Fin, Lohja, VT25
SE, Norsholm, E4
SE, Svaneberg, E20
NL, Spaarnwoude, A9
NL, Nieuwegein, A2
UK, Reading, M4
UK, Oxford, M40
0
Fig. 2 Cd concentration in groundwater
Cr is a metal that tends to accumulate in the soils due to its low mobility. Its presence in
areas far from the road denotes atmospheric pollution (Ward, 1990a).
Variação de Cr (mg/kg) em solos adjacentes a estradas, a 3 distâncias e 3 profundidades
Cr (mg/kg) variation in soils close to the road, at 3 distances and 3 depths
- 26study
casos cases;10
de estudo; countries
10 países (P,
SP, F, I, D, SW, NL, DK, UK, FIN) - 26
(P,SP,F,I,D,SW,NL,DK,UK,FIN)
-
400
Valor de
Intervenção
Intervention
value
(380 mg/kg)
(380 mg/kg)
max.
máx
upper quartile
300
quartil sup.
median
mediana
lower
quartil
inf.quartile
.
mín
min.
200
Valor guia 100
Target value (100 mg/kg)
(100 mg/kg)
0 -1 m
1-5m
depth
2-10 cm prof.
0-2 cm depth
prof.
depth
10-30 cm prof.
2-10 cm depth
prof.
0-2 cm depth
prof.
10-30 cm depth
prof.
2-10 cm prof.
depth
0-2 cm depth
prof.
0
20 - 30 m
Fig. 3 Cr variation in soils close to the road, at 3 distances and 3 depths
5
Cr concentrations in the soils of 26 case-studies are below intervention values defined
in Dutch legislation. Nevertheless, the target value is frequently overcome.
In some of the case-studies it is possible to observe the decrease in Cr concentration with
the distance to the road and in depth, but other cases show the opposite pattern. Usually Cr
concentration is quite constant along the depth and distance showing a low capacity for
mobilization to the groundwater (cf. Fig. 3). This is also evidenced by the low concentration
of Cr in water (all lower than 5 µg/l). Fig. 4 shows the concentration found in the vadose zone
water. Groundwater concentration for the same studies show concentrations above detection
limit in few cases.
50
Cr (µ
µg/l)
45
40
VMA = 50 µg/l (30 µg/l)
VMR = - (1 µg/l)
35
(Dutch legislation,
30
MHSPE, 1994)
25
20
15
10
5
3.9
0.8
15 - 40 m
0.00
1-5 m
0-1 m
P, Vila Real, IP4
Fin, Utti, VT6
D, Vejenbrod, M14
Fin, Lohja, VT25
SE, Norsholm, E4
SE, Svaneberg, E20
NL, Spaarnwoude, A9
UK, Oxford, M40
NL, Nieuwegein, A2
UK, Reading, M4
2.5
F, Houdan, RN12
0.7
P, Recta do Cabo, EN10
1.1 1.8
D, Rud, M70
3
0
F, Erdre, A11
5
April - June 99
Jan - March 99
Oct - Dec 98
July - Set 98
Fig. 4 Cr concentration in the vadose zone
Cu is a low mobility metal, especially in areas with some organic matter content, not
significantly influenced by changes in pH or salt content. It is one of the metals found
connected to road pollution (DWW, 1995; Reinirkens, 1996; Leitão et al., 2000 &
Diamantino, 2002).
Cu concentration in the soils analysed are frequently above the target value, specially in
the first soil horizon and close to the road. However the intervention value is unusually
6
overcome (cf. Fig. 5). It is also clear the decrease of Cu with distance and depth in several
case-studies individually.
Variação de Cu (mg/kg) em solos adjacentes a estradas, a 3 distâncias e 3 profundidades
Cu (mg/kg) variation in soils close to the road, at 3 distances and 3 depths
casos
de estudo;
10 países
(P, SP, F, I, D, SW, NL, DK, UK, FIN) -- 37- 37
study
cases;10
countries
(P,SP,F,I,D,SW,NL,DK,UK,FIN)
240
200
Valor de Intervenção
Intervention(190
value
mg/kg)
(190 mg/kg)
160
max.
máx
upper quartile
quartil sup.
median
mediana
120
lower quartile
quartil inf.
mín.
min.
80
Target value
(36 mg/kg)
Valor guia
(36 mg/kg)
40
0 -1 m
1-5m
depth
2-10 cm prof.
depth
0-2 cm prof.
depth
10-30 cm prof.
2-10 cm depth
prof.
0-2 cm depth
prof.
depth
10-30 cm prof.
depth
2-10 cm prof.
depth
0-2 cm prof.
0
20 - 30 m
Fig. 5 Cu variation in soils close to the road, at 3 distances and 3 depths
80
Cu (µ
µg/l)
86
70
60
VMA = 50 µg/l (75 µg/l)
VMR = 20 µg/l (15 µg/l)
50
(Dutch legislation,
MHSPE, 1994)
40
33
30
23
20
10
15 - 40 m
1-5 m
P, Vila Real, IP4
P, Recta do Cabo, EN10
F, Houdan, RN12
D, Rud, M70
0-1 m
F, Erdre, A11
Fin, Utti, VT6
D, Vejenbrod, M14
Fin, Lohja, VT25
SE, Norsholm, E4
SE, Svaneberg, E20
NL, Spaarnwoude, A9
UK, Oxford, M40
NL, Nieuwegein, A2
UK, Reading, M4
0
April - June 99
Jan - March 99
Oct - Dec 98
July - Set 98
Fig. 6 Cu concentration in the vadose zone
7
Concerning the Cu water concentration, several values are higher than VMR, but all except
one are below VMA. The higher values are closer to the road (cf. Fig. 6).
Pb is one of the metals more studied under road pollution. Soil analysis during the last 25
years has shown changes in the decrease of Pb due to the consumption of unleaded gasoline.
Pb mobility is dependent on the presence of carbonates, Fe-Mn oxydes and to organic
compounds. Their presence favours the Pb accumulation in the soil and limits its capacity to
be leached (DWW, 1995).
Pb (mg/kg) variation in soils close to the road, at 3 distances and 3 depths
Variação de Pb (mg/kg) em solos adjacentes a estradas, a 3 distâncias e 3 profundidades
1000
- 37 casos de estudo; 10 países (P, SP, F, I, D, SW, NL, DK, UK, FIN) -
- 37 study cases;10 countries (P,SP,F,I,D,SW,NL,DK,UK,FIN) -
800
max.
máx
upper
quartil
sup.
quartile
lower quartile
mediana
median
600
quartil inf.
mín.
min.
Intervention value
Valor de Intervenção
(530 mg/kg) (530 mg/kg)
400
200
Target value
(85 mg/kg)
Valor guia
(85 mg/kg)
0 -1 m
1-5m
10-30 cm depth
prof.
2-10 cm prof.
depth
0-2 cm depth
prof.
depth
10-30 cm prof.
2-10 cm prof.
depth
0-2 cm depth
prof.
10-30 cm depth
prof.
depth
2-10 cm prof.
0-2 cm prof.
depth
0
20 - 30 m
Fig. 7 Pb variation in soils close to the road, at 3 distances and 3 depths
In most case-studies, the Pb concentration in soils is quite high, several exceeding the
intervention value. For waters, the presence of Pb is clear, but below VMA.
In most case-studies it is observed a diminution of Pb with the distance to the road and in
depth (cf. Fig. 7).
In 10 of the 14 case-studies analysed under POLMIT project, the water in the vadose zone
had concentrations below 10 µg/l. In some places there are significant changes during the
8
year. Also groundwater has concentrations below VMA, and the pattern of concentrations is
very dependent of soil conditions (cf. Fig. 8).
50
Pb (µ
µg/l)
45
July - Sept. 98
Oct. - Dec. 98
Jan. - Mar-99
April - Jun-99
40
35
30
25
VMA = 50 µg/l (75 µg/l)
VMR = (15 µg/l)
20
15
(Dutch legislation
10
MHSPE, 1994)
5
P, Vila Real, IP4
P, Recta do Cabo, EN10
F, Houdan, RN12
D, Rud, M70
F, Erdre, A11
D, Vejenbrod, M14
Fin, Utti, VT6
SE, Norsholm, E4
SE, Svaneberg, E20
NL, Spaarnwoude, A9
NL, Nieuwegein, A2
UK, Reading, M4
UK, Oxford, M40
0
Fig. 8 Pb concentration in groundwater
Zn is a very mobile element especially in sandy and acid soils. Pagotto et al. (2001) refers
to a particular sensitivity of Zn to pH decrease, with a consequent mobilization of this metal.
Zn concentration in soils is higher than the target value for the 3 depths and 3 distances
analysed, in several case-studies (cf.
Fig. 9). It is also clear a decrease in concentration with distance to the road and depth,
although that is not the case in many individual case-studies.
The existence of Zn in groundwater varies from case to case, depending on the existing
physico-chemical conditions. Some authors found almost no evidence of Zn pollution
(Reinirkens, 1996) but most Fig. 10 found the opposite. However, values are below VMA.
9
Zn (mg/kg) variation in soils close to the road, at 3 distances and 3 depths
Variação de Zn (mg/kg) em solos adjacentes a estradas, a 3 distâncias e 3 profundidades
casoscases;10
de estudo; countries
10 países (P,(P,SP,F,I,D,SW,NL,DK,UK,FIN)
SP, F, I, D, SW, NL, DK, UK, FIN) - 37- 37study
-
1000
800
Valor de Intervenção
(720 mg/kg)
Intervention value
(720 mg/kg)
máx
max.
upper
quartil
sup.quartile
600
mediana
median
lower
quartil
inf.
mín.
quartile
min.
400
200
Target value
Valor guia
(140 mg/kg)(140 mg/kg)
0 -1 m
1-5m
2-10 cm prof.
depth
0-2 cm prof.
depth
10-30 cm depth
prof.
2-10 cm prof.
depth
0-2 cm prof.
depth
10-30 cm prof.
depth
2-10 cm prof.
depth
0-2 cm prof.
depth
0
20 - 30 m
Fig. 9 Zn variation in soils close to the road, at 3 distances and 3 depths
500
450
July - Sept. 98
Oct. - Dec. 98
Jan. - Mar-99
April - Jun-99
400
350
300
250
VMA = 3000 µg/l (720 µg/l)
VMR = 500 µg/l (140 µg/l)
200
150
(Dutch legislation
MHSPE, 1994)
100
50
P, Vila Real, IP4
P, Recta do Cabo, EN10
F, Houdan, RN12
F, Erdre, A11
D, Rud, M70
D, Vejenbrod, M14
Fin, Utti, VT6
SE, Norsholm, E4
SE, Svaneberg, E20
NL, Spaarnwoude, A9
UK, Oxford, M40
NL, Nieuwegein, A2
0
UK, Reading, M4
Zn (µ
µg/l)
Fig. 10 Zn concentration in groundwater
10
SYNTHESIS AND CONCLUSIONS
Road pollution is a source of diffuse pollution that can affect the soil and water in its vicinity.
The effects of runoff discharge in the environment usually do not led to acute pollution
effects. The long term effects, namely of heavy metals, are the ones that can cause soil and
water degradation.
The 37 case-studies analysed have shown the long term effects of heavy metals road
pollution in soils. The direct effects of road pollution are spatially limited to the soils adjacent
to roads, in the areas of car splash, usually influencing a strip narrower than 25 m (García e
Millán, 1994; Reinirkens, 1996). However, other authors (Ward e Savage, 1994) confirm a
significant increase of soil metal content up to 100 m from the road (London M25).
In most cases, heavy metal pollution decreases with the distance to the road (García e
Millán, 1994). Also the first soil horizon is the more polluted one in term of heavy metals (cf.
Ward, 1990a).
Road pollution is dependent of the traffic level but a direct correlation is not possible due
to the influence of other factors such as wind direction, precipitation pattern, age of the road,
topography, pH, CEC, soil organic matter content, etc.
Among the main heavy metals causing pollution are Pb, Zn and Cu. Ni and Cr do not
influence in a relevant way the soil quality in the areas close to the roads. Several other heavy
metals are under study at the present.
Cd, being a mobile element, is produced in low concentrations. Pb and Cu are produced in
higher quantities but their mobilization is difficult; only for low pH conditions or as a soluble
complex it is possible to mobilize them in a significant way. Zn is emitted in considerable
quantities, especially when zinc crash barriers exist, and can be very mobile in acid
conditions.
11
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